tuning failed for SDR50

[litzchee]

I am using an iMX8qxp on my custom board and I am experiencing tuning failed error when inserting a SDR50 SD card. This issue does not happen when I insert a SDR104 card.

Here is the device tree configuration

usdhc2: mmc@5b020000 {
		interrupts = <GIC_SPI 233 IRQ_TYPE_LEVEL_HIGH>;
		reg = <0x5b020000 0x10000>;
		clocks = <&sdhc1_lpcg 1>,
			 <&sdhc1_lpcg 0>,
			 <&sdhc1_lpcg 2>;
		clock-names = "ipg", "per", "ahb";
		assigned-clocks = <&clk IMX_SC_R_SDHC_1 IMX_SC_PM_CLK_PER>;
		assigned-clock-rates = <200000000>;
		power-domains = <&pd IMX_SC_R_SDHC_1>;
		fsl,tuning-start-tap = <20>;
		fsl,tuning-step= <2>;
		status = "disabled";
	};

&usdhc2 {
	assigned-clocks = <&clk IMX_SC_R_SDHC_1 IMX_SC_PM_CLK_PER>;
	assigned-clock-rates = <200000000>;
	pinctrl-names = "default", "state_100mhz", "state_200mhz";
	pinctrl-0 = <&pinctrl_usdhc2>, <&pinctrl_usdhc2_gpio>;
	pinctrl-1 = <&pinctrl_usdhc2_100mhz>, <&pinctrl_usdhc2_gpio>;
	pinctrl-2 = <&pinctrl_usdhc2_200mhz>, <&pinctrl_usdhc2_gpio>;
	bus-width = <4>;
	vmmc-supply = <&reg_usdhc2_vmmc>;
	cd-gpios = <&lsio_gpio4 22 GPIO_ACTIVE_LOW>;
	wp-gpios = <&lsio_gpio4 21 GPIO_ACTIVE_HIGH>;
	status = "okay";
};

I am wondering if trace length has something to do with this error. This is because previously I have tried on another board also using iMX8, but the SD card slot is nearer to the processor. In this case, I did not encounter any tuning failure for both SDR50 and SDR104

If trace length is the issue, what parameters I can tweak? Thanks

[Rita_Wang]

How about your usdhc2 hardware design? For the SD card design, for the IO power is 1.8V or 3.3V?